You might want to try taking him into the shower with you? Lots of birds enjoy the spray from the shower
You can buy special shower perches that stick to the tiles too.
It might be a good idea to also get him some multi-vits to add to the water which should help.
Birds should always have a minimun of 2 sprays a week for healthy feathers.
Try adding some Aloe Vera to the water when you spray him, this will also help the condition of his feathers.
My cockatiels also love to eat cooked corn, fresh cocount, red pepper and grapes
